Weeks 4 & 5 Indigo Synthesis

Transcription

1 Weeks 4 & 5 Indigo Synthesis I believe that the great Creator has put ores and oil on this earth to give us a breathing spell. As we exhaust them, we must be prepared to fall back on our farms, which is God s true storehouse and can never be exhausted. We can learn to synthesize material for every human need from things that grow. George Washington Carver Scientist An understanding of the transformation of matter is fundamental to the study of chemistry. The synthesis of new molecules and new materials is the basis of the chemical industry. The synthesis of new chemicals involves a number of different linked processes. First, reactions are performed that generate new chemicals. Then the products are isolated from the other materials present, purified and characterized. This last procedure involves measurement of their chemical and physical properties to confirm their identity and purity. This two-week experiment is designed to introduce you to some of the issues involved in transforming matter. You will investigate the synthesis of the dye indigo. This common dye will be made, isolated and evaluated. Educational Objectives: A student who has successfully completed this experiment will be able to synthesize indigo, determine percent yield for a reaction, make leuco-indigo from indigo, dye cloth using vat dying, perform a sulfonation reaction, and use absorption spectroscopy to determine yield. Experimental Objectives: A student who performs this experiment is asked to synthesize indigo from smaller precursors, isolate the indigo using filtration and determine a yield, prepare leucoindigo and use it to dye a cloth test strip, synthesize indigo carmine from indigo, and quantify the indigo carmine produced using absorption spectroscopy. Background Indigo is the name given to an organic molecule with an intense blue color and to the plant (a member of the pea family) from which it is extracted. Indigo has been used to dye cotton and wool fabric for millennia. It is the source of the color in blue jeans. The molecule was first made synthetically in By the turn of the 20 th century a commercial process had been developed and synthetic production quickly replaced agricultural production. Synthesizing Indigo Many different ways are now known to make indigo. The one presented here is quick and produces indigo in very high yield. The reaction is between 2 nitrobenzaldehyde (a.k.a. o-nitrobenzaldehyde or orthonitrobenzaldehyde) and acetone in the presence of a strong base (NaOH). 2 C 7 H 5 NO C 3 H 6 O C 16 H 10 N 2 O CH 3 CO 2 H + 2 H 2 O (2-1) 2-nitrobenzaldehyde acetone indigo acetic acid

2 The organic molecules are dissolved in water. A NaOH solution is added to start the reaction. Since indigo is virtually insoluble in water, it precipitates as fast as it forms. The product can be readily collected by filtration and quantified. Dying Cloth Indigo s insolubility in water not only makes it easily to isolate, but also makes it a good dye. Once impregnated in the cloth, washing with water will not easily dislodge the dye molecules. Getting the dye into the cloth, however, is a problem. Fortunately, the chemistry of indigo provides a solution. Indigo can be reduced to form a compound known as leucoindigo. Equation 2 shows half of the reaction for this reduction. It can be coupled with any suitable reaction that provides the two electrons. C 16 H 10 N 2 O H + + 2e C 16 H 12 N 2 O 2 (2-2) indigo leucoindigo Leucoindigo is a colorless molecule that is quite soluble in water. To dye cloth, indigo is reduced to leucoindigo with an appropriate reagent and dissolved in water. The cloth to be dyed is then dipped into the solution. When the cloth is removed from the solution and allowed to dry, the oxygen in the air will oxidize the leucoindigo to indigo. Simultaneously, the dye becomes fixed in the cloth and the color appears. A suitable reaction to provide the needed electrons is the oxidation of the stannite ion to stannate. This is the reaction that will be available for you to use. SnO 2 2- stannite ion H 2 O SnO H + + 2e (2-3) stannate ion Making Indigo Carmine Although indigo itself is quite insoluble in water, it can be reacted with sulfuric acid to produce watersoluble forms that retain the characteristic intense blue color. When placed in a concentrated solution of sulfuric acid, the indigo will add two, three or four sulfonic acid (HSO 3 ) units. The actual number will depend on the strength of the acid, the temperature and the reaction time. C 16 H 10 N 2 O H 2 SO 4 2 C 16 H 8 N 2 O 8 S 2 Indigo sulfuric acid indigo disulfonic acid C 16 H 10 N 2 O H 2 SO 4 3 C 16 H 7 N 2 O 11 S 3 indigo trisulfonic acid + 2 H 2 O + 2 H + (2-4) + 3 H 2 O + 3 H + (2-5) 4 C 16 H 10 N 2 O H2SO4 C 16 H 6 N 2 O 14 S H 2 O + 4 H + (2-6) indigo tetrasulfonic acid The disulfonic acid form is extensively used in industry. As a dye in the food and drug industry, it is known as FD&C Blue #2. It is also used as a functional kidney test and to color nylon surgical sutures. One gram of indigo carmine will dissolve in about 100 ml of water.

3 The Problem The problem put to your group is to investigate the properties of the organic dye indigo. The process you will use can be summarized as follows. 1. Make some indigo. 2. Isolate the indigo and determine a yield. 3. Convert some of the indigo into leucoindigo and use that to dye a cloth sample. 4. Convert the remaining indigo into indigo carmine and determine the yield using absorption spectroscopy. The first three activities will be performed the first week. Your charge is to determine the efficiency of this synthesis method in preparing indigo. Indigo carmine will be synthesized the second week. But indigo carmine is only one of three possible products. In fact, the extent of the reaction and the mixture of products will be affected by the conditions under which the reaction is performed. Your group is asked to evaluate the effect of one of the following conditions on the extent of reaction and the mixture of products: strength of the acid, the temperature and the reaction time. Procedures Making Indigo The quantities given here are intentionally small. Larger quantities of the indigo can be made by proportionately increasing the amounts. You will need to write procedures in your lab notebook based on the descriptions given here. Parts of these procedures will be used as answers to the TA-graded pre-lab questions. Don t worry about having correct procedures. You will have the chance to modify them based on what you learn during the pre-lab discussion. Here s a short video of indigo being made. Indigo is a highly colored dye. Very small amounts can impart lots of color to all kinds of things (clothing, hands, books, etc.). Be careful to avoid coloring things best left uncolored. Write a procedure for making indigo. Incorporate the following features. Use approximately 0.4 g of 2-nitrobenzaldehyde. This is a solid reagent. Use about 5 ml of acetone. This is a liquid reagent. Dissolve the nitrobenzaldehyde in the acetone and then add the NaOH. You should use about 6 ml of 1.0M NaOH. You will need to add the NaOH slowly the reaction generates a lot of heat. Don t add the NaOH so fast that the acetone evaporates. After thoroughly mixing these chemicals you will need to allow the mixture to sit for at least 5 minutes to ensure the reaction is complete. Isolate the indigo using vacuum filtration as described in chapter 5-2 of the lab book. Allow the indigo to dry. When it s dry you can determine the mass. Characterizing Indigo: Dyeing Cloth

4 Indigo is used to dye cloth in a process known as vat dyeing. The indigo is first converted to the watersoluble leucoindigo (2-2). The cloth is then dipped into a solution of the leucoindigo, allowed to soak, removed, and allowed to dry. As the cloth dries, oxygen from the air oxidizes the leucoindigo back to indigo, and in the process, also fixes the indigo in the cloth. Preparation of leucoindigo is a two-step process. First, the reductant must be made, then the leucoindigo prepared. The reductant provided for your use is the sodium stannite reagent. Because it is a strong reductant, it easily reacts with atmospheric oxygen. Thus, it must be prepared fresh every time it is used. Here s how. Sodium Stannite Reagent Put one gram of stannous chloride dihydrate in a small beaker (150 ml). Add 10 ml of 1 M HCl and swirl to dissolve. This should take a few minutes. Don t worry if the solution is cloudy. Add 20 ml of 3 M NaOH. Swirl to mix. At first a white to off-white precipitate will form. It should re-dissolve with mixing. Again, this should take a few minutes. Don t worry if the final solution is slightly cloudy. This solution is the stannite reagent. Preparation of Leucoindigo Place half of the indigo you made earlier in a small beaker. Save the other half for next week. Add 3 ml of a 3 M NaOH solution. Heat to boiling in a hot water bath. Slowly add stannite reducing reagent, with constant stirring. The indigo dissolves rather slowly. The stannite reagent should be added a ml or so at a time, with mixing, until a total of 25 ml has been added. Continue to heat and stir for another 10 minutes. Take a clean small beaker (150 ml) and add 25 ml of distilled water. Gravity filter the leucoindigo solution, collecting the filtrate in this beaker. The dilute filtrate is what you will use to dye the cloth. Work a small piece of cloth into the dye solution and allow it to soak. When saturated, remove and allow it to drain and dry. Note that the leucoindigo cannot be reoxidized until the cloth has dried out. Once the cloth is dry, the color will slowly develop. Making Indigo Carmine Performing the Reaction In addition to reacting with concentrated sulfuric acid, indigo is also soluble in this reagent. Thus, the reaction system is rather simple. Solid Remember that concentrated sulfuric acid, like all concentrated acids, is strongly corrosive and will cause the immediate destruction of clothing and skin. Should you suspect you ve gotten some on you, begin washing with water immediately and consult your instructor. Make sure all spills are neutralized and cleaned up immediately. Figure 2-1. Cloth swatch for testing indigo.

5 indigo is dissolved in 18 M H 2 SO 4 and the mixture heated to promote the reaction. After a sufficient period of time, the reaction can be stopped by the addition of water which will also dilute the sulfuric acid and the un-reacted indigo will precipitate out. The following is an outline of a procedure for evaluating this reaction. You should use your remaining indigo for this procedure. It should be at least 0.05 g. If you don t have enough consult your instructor. Dissolve the indigo in concentrated sulfuric acid (H 2 SO 4 ). You should use 20 drops (1 ml) for every 0.1 g of indigo you have with a minimum amount of 1 ml. Swirl to dissolve the indigo in the acid. Heat in a simmering water bath. How long depends on what you and your group decide on but it should be for at least 10 minutes and not longer than 30. When it is time to stop, pour the reaction mixture into distilled water. But first, cool the solution. Use 5 ml of water for every ml of acid you started with. The unreacted indigo will precipiatate leaving the sulfonated products dissolved in the water. Set up a clean vacuum filtrate apparatus. Do not add water to acid. You can get a steam explosion. Pour the acid into water. And do not pour hot acid into water. Again, a potential explosion. Remember that you will be keeping the filtrate. Filter the indigo solution. Use a small amount of distilled water to wash all solution through the funnel. You may discard the solid, un-reacted indigo residue. Determine the volume of your filtrate. A graduated cylinder is sufficient for this measurement. Spectrophotometric Determination of Product Yield You will be evaluating your product using absorption spectroscopy. Since you want to know the total moles you will need to know both the molarity and the total volume. You will need to develop a procedure to determine the λ max and the absorbance. Remember that if the absorbance is more than 1.0 you will need to dilute the solution. Finally, you will need to know the molar absorptivity for all the appropriate indigo sulfonate known solutions. Data Analysis and Report Considerations Data Analysis For the synthesis of indigo you will need to determine your percent yield which is discussed in chapter 2-4 of the lab book. This will require figuring out the experimental yield and the yield theoretical yield which is best done while still in lab in collaboration with your fellow group members. For the synthesis of indigo carmine, determine your percent yield. Again you will need to know the experimental yield and the theoretical yield. And again, this is best done while still in the lab in collaboration with your fellow group members. For the synthesis of indigo carmine you will also have to evaluate which of the three sulfonated indigo carmines you made. This will be done by evaluating the spectrum of your product solution.

The Chemistry of Dyes Part I: The Synthesis of Indigo Dye Name: Period: PURPOSE: To synthesize indigo dye in preparation for understanding how and why it dyes fabrics THEORY: Organic Chemistry is the study

CHEMICAL REACTIONS OF COPPER AND PERCENT YIELD Objective To gain familiarity with basic laboratory procedures, some chemistry of a typical transition element, and the concept of percent yield. Apparatus

Chemistry 111 Lab: Percent Composition Page D-3 DETERMINATION OF THE PERCENT COMPOSITION OF A MIXTURE In this experiment you are to determine the composition of a mixture containing unknown proportions

Cautions Nitric acid and sulfuric acid are toxic and oxidizers and may burn your skin. Nitrogen dioxide gas produced is hazardous if inhaled. Sodium hydroxide is toxic and corrosive and will cause burns

Name: Section: Experiment 4: Synthesis of Alum Pre-laboratory Assignment (Read through the experiment before starting!) 1. a) What are the strong acid and strong base used in this synthesis? b) What should

THREE CHEMICAL REACTIONS 1 NOTE: You are required to view the podcast entitled Decanting and Suction Filtration before coming to lab this week. Go to http://podcast.montgomerycollege.edu/podcast.php?rcdid=172

DYES AND DYEING 2003 by David A. Katz. All rights reserved. Permission for classroom use provided original copyright is included. Dyeing of textiles has been practiced for thousands of years with the first

EXPERIMENT 29 SYNTHESIS OF ASPIRIN INTRODUCTION Aspirin is one of the most widely used medications in the world. It is employed as an analgesic (pain relief), an anti-pyretic (fever control) and an anti

Experiment 2 Purification by Recrystallization Objectives 1) To be able to select an appropriate recrystallizing solvent. 2) To separate and purify acetanilide by recrystallization. 3) To compare the melting

Recovery of Elemental Copper from Copper (II) Nitrate Objectives: Challenge: Students should be able to - recognize evidence(s) of a chemical change - convert word equations into formula equations - perform

Experiment No. Date OXIDATION-REDUCTION TITRATIONS-Permanganometry INTRODUCTION Potassium permanganate, KMnO 4, is probably the most widely used of all volumetric oxidizing agents. It is a powerful oxidant

Experiment 3 Separation by Solvent Extraction Objectives To separate a mixture consisting of a carboxylic acid and a neutral compound by using solvent extraction techniques. Introduction Frequently, organic

Synthesis of a Coordination Compound Containing Iron and Analysis of this Compound Using Redox Methods Prelab Name Total /10 NOTE: AT THIS POINT YOU WILL ANSWER ALL PRELAB QUESTIONS IN YOUR CARBON COPY

Chemistry 1215 Experiment #10 The Reaction of Zinc and Iodine: The Combination of Two Elements Objective The objective of this experiment is to perform a combination reaction by reacting elemental zinc

Name Lab Partner(s) Section Date: Carbonate to Halide Conversion Objective The theoretical yield of the reaction product and the ratio of products to reactants will be predicted using the Law of Conservation

EXPERIMENT 4: Separation of a Mixture of Solids Read the entire experiment and organize time, materials, and work space before beginning. Remember to review the safety sections and wear goggles when appropriate.

Chemistry 1215 Experiment #9 Copper and its Compounds Objective The objective of this experiment is to take a piece of copper as efficiently as possible through a series of chemical reactions. The final

1 Amino Acids, Peptides, and Proteins Introduction Amino Acids Amino acids are the building blocks of proteins. In class you learned the structures of the 20 common amino acids that make up proteins. All

EXPERIMENT 7 Reaction Stoichiometry and Percent Yield INTRODUCTION Stoichiometry calculations are about calculating the amounts of substances that react and form in a chemical reaction. The word stoichiometry

(adapted from Blackburn et al., Laboratory Manual to Accompany World of Chemistry, 2 nd ed., (1996) Saunders College Publishing: Fort Worth) Purpose: To prepare a sample of soap and to examine its properties.

AN EXPERIMENT IN ALCHEMY: COPPER TO SILVER TO GOLD 2005, 2000, 1996, 1979 by David A. Katz. All rights reserved INTRODUCTION One of the goals of the ancient alchemists was to convert base metals into gold.

IDENTIFICATION OF AN UNKNOWN ORGANIC COMPOUND Classification Tests In this experiment you will attempt to identify an organic unknown from a selected group of compounds from the class of alcohols, aldehydes,

Purpose Experiment 7 GRAVIMETRIC ANALYSIS OF A TWO COMPONENT MIXTURE The purpose of the experiment is to determine the percent composition by mass of a two component mixture made up of NaHCO 3 and Na 2

Aspirin Synthesis Experiment 5 Aspirin is the common name for the compound acetylsalicylic acid, widely used as a fever reducer and as a pain killer. Salicylic acid, whose name comes from Salix, the willow

Synthesis, Isolation, and Purification of an Ester AP Chemistry Laboratory Introduction An ester is a chemical compound that is formed when an organic acid reacts with an alcohol. Esters frequently have

Coordination Compounds with Copper (II) Prelab (Week 2) Name Total /10 SHOW ALL WORK NO WORK = NO CREDIT 1. What is the purpose of this experiment? 2. Write the generic chemical formula for the coordination

CHEMICAL DETERMINATION OF EVERYDAY HOUSEHOLD CHEMICALS Cautions: You will be using dangerous, caustic (corrosive) chemicals in this lab, so it is important that you are very careful with them. Wear gloves

Experiment 5 Preparation of yclohexene In this experiment we will prepare cyclohexene from cyclohexanol using an acid catalyzed dehydration reaction. We will use the cyclohexanol that we purified in our

The Empirical Formula of a Compound Lab #5 Introduction A look at the mass relationships in chemistry reveals little order or sense. The ratio of the masses of the elements in a compound, while constant,

Physical and Chemical Properties and Changes An understanding of material things requires an understanding of the physical and chemical characteristics of matter. A few planned experiments can help you

Lab 6 Two Weeks Characterization of Inorganic Compounds* *Taken from an Inorganic Lab course offered at Purdue University Chemical & Engineering News reported the levels of production for industrial chemicals

1) Error Analysis Apparatus Errors (uncertainty) Every time you make a measurement with a piece of apparatus, there is a small margin of error (i.e. uncertainty) in that measurement due to the apparatus

AP Chemistry Lab Date: Chemist: Lab Write Up Due Date: Lab 1: Gravimetric Analysis of a Metal Carbonate BACKGROUND How do chemists determine the identity of a compound? A large variety of analytical techniques

DETERMINATION of the EMPIRICAL FORMULA One of the fundamental statements of the atomic theory is that elements combine in simple whole number ratios. This observation gives support to the theory of atoms,

Experiment 8: Synthesis and Analysis of an Inorganic Compound CH3500: Inorganic Chemistry, Plymouth State University Adapted from Johnson, R.C. "Convenient procedure for the preparation of potassium trioxalatoferrate(iii),"

Experiment 8 Synthesis of Aspirin Aspirin is an effective analgesic (pain reliever), antipyretic (fever reducer) and anti-inflammatory agent and is one of the most widely used non-prescription drugs. The

Experiment 10 ANALYSIS OF PHOSPHORUS IN PLANT FOOD Adapted by Ross S. Nord, Eastern Michigan University, from Analysis of Phosphorous in Fertilizer found at http://chem.lapeer.org/chem2docs/phosphateanal.html

Group A Cation Analysis Inorganic Qualitative Analysis Inorganic qualitative analysis is the unambiguous identification of cations (and/or anions) which are present in a given solution. Unique tests for

How are drugs developed? Take part in the research of a drug Experiment workshop Student guide 1 Introduction Many stages are involved in the discovery and development of medicines. One of the most important

Experiment 8. Determination of the Molar Mass of an Unknown Acid by Acid-Base Titration In this experiment you will: Prepare and standardize a solution of sodium hydroxide Determine the molecular weight

Extraction: Separation of Acidic Substances Chemists frequently find it necessary to separate a mixture of compounds by moving a component from one solution or mixture to another. The process most often

Water Lab I. Distillation Hypothesis: Water can be purified by distillation. Objective: To distill samples of water that contains volatile and nonvolatile components. Materials and Equipment: Sodium chloride,

STOICHIOMETRY: The Reaction of Iron with Copper (II) Sulfate Introduction In this experiment we will use stoichiometric principles to deduce the appropriate equation for the reaction between metallic iron

Oxidation of Isoborneol to Camphor Organic Redox A simple way to think about organic redox is that it is really an increase in the electronegativity or electropositivity of carbon due to functional group

Preparation of an Alum Pages 75 84 Pre-lab = pages 81 to 82, all questions No lab questions, a lab report is required by the start of the next lab What is an alum? They are white crystalline double sulfates

1 Experiment 4: Synthesis of Alum from Scrap Aluminum Objective: In this experiment, you will be converting the aluminum metal from a beverage can into the chemical compound potassium aluminum sulfate,

ISLATIN F CAFFEINE FRM TEA Introduction In this experiment, caffeine is isolated from tealeaves. The chief problem with the isolation is that caffeine does not exist alone in the tealeaves, but other natural

Ms. Sonderleiter AP Chemistry Name: Date: Lab #1: Determining the Empirical Formula of a Compound Background: How did early chemists ever manage to determine the chemical formulas of compounds? What kind

CHEMICAL DETERMINATION OF EVERYDAY HOUSEHOLD CHEMICALS Purpose: It is important for chemists to be able to determine the composition of unknown chemicals. This can often be done by way of chemical tests.

AN EXPERIMENT IN ALCHEMY: COPPER TO SILVER TO GOLD 2005, 2000, 1996 by David A. Katz. All rights reserved INTRODUCTION One of the goals of the ancient alchemists was to convert base metals into gold. Although

Thermochemistry Experiment 10 Thermochemistry is the study of the heat energy involved in chemical reactions and changes of physical state. Heat energy is always spontaneously transferred from hotter to

Experiment 8 Preparation of Cyclohexanone by ypochlorite xidation In this experiment we will prepare cyclohexanone from cyclohexanol using hypochlorite oxidation. We will use common household bleach that

Chemistry 151 Last updated Dec. 2012 Lab 6: Percent Composition and Empirical formulas Introduction In this lab, you will experimentally determine the percent composition of a copper chloride, which you

Lab 4 Taking Apart the Pieces How does starting your morning out right relate to relief from a headache? I t is a lazy Saturday morning and you ve just awakened to your favorite cereal Morning Trails and

Experiment 15 Vitamins Part 1: Solubility of Vitamins Vitamins are organic compounds that are required as cofactors for specific enzymes. They are not synthesized in the body and therefore must be obtained

EXPERIMENT II STABILIZATION OF RARE OXIDATION STATE-TRIS(THIOUREA) COPPER(I) SULFATE When an element can exist in more than one oxidation state in aqueous solution, each oxidation state will have different

1 Recrystallization Introduction Solubility Most compounds are more soluble in a given solvent at higher temperatures. As you can see from the data in the table below, the solubilities in water of salt

Title: Training Lab 1 Chemistry 11100, Fall 2012 Introduction The purpose of this lab is to introduce you to a series of techniques that you will use in chemistry lab. For this lab, you will be using the

EXPERIMENT 12: Empirical Formula of a Compound INTRODUCTION Chemical formulas indicate the composition of compounds. A formula that gives only the simplest ratio of the relative number of atoms in a compound

1 EXPERIMENT B7: GREEN CRYSTAL Learning Outcomes Upon completion of this lab, the student will be able to: 1) Synthesize an inorganic salt and purify it using the method of recrystallization. 2) Test the

1 Breathalyzer Reaction Introduction A breathalyzer (breath analyzer) is a device for estimating blood alcohol content (BAC) from a breath sample. The invention of the breathalyzer provided law enforcement

Properties of Acids and Bases Identification and Classification Introduction Acids and bases are useful reagents in the chemistry laboratory and play an important role in biology and nature. What are acids

Thermochemistry: Enthalpy of Reaction Hess s Law Objective Demonstrate Hess s Law for determining the enthalpy of formation for MgO by measuring temperature change for several reactions. Introduction The

Suggested Solutions to student questions(soap) 1. How do you explain the cleansing action of soap? The ionic part of the soap molecule is water-soluble while the non-polar hydrocarbon part is soluble in

3-1 Experiment 3 Limiting Reactants Introduction: Most chemical reactions require two or more reactants. Typically, one of the reactants is used up before the other, at which time the reaction stops. The

1 Experiment 7: Titration of an Antacid Objective: In this experiment, you will standardize a solution of base using the analytical technique known as titration. Using this standardized solution, you will

Recrystallization (or Crystallization) is a technique used to purify solids. This procedure relies on the fact that solubility increases as temperature increases (you can dissolve more sugar in hot water

ACTIVITY BRIEF Dyes: Industrial scale up The science at work Only small quantities of dyes can be extracted or synthesised in the laboratory. However, scaling up to industrial scale presents various problems.

THE SCIENCE OF SOAPS AND DETERGENTS 2000 by David A. Katz. All rights reserved Reproduction permitted for educational purposes as long as the original copyright is included. INTRODUCTION A soap is a salt